There are many applications that require the determination of the time for a digital bit or bit stream to traverse a round-trip path from a source transceiver to a destination transceiver and back. Such determinations are helpful for example, for sensing the proximity of one object having one transceiver attached to it relative to another object having the other transceiver attached to it. Application areas include, but are not limited to, distance measurement, indoor positioning, emergency location, search and rescue, personnel accountability systems, security systems, collision warning, adaptive cruise control, intelligent transportation systems, logistics, robotics, network analysis, communication channel characterization, and others.